Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist has been carried out. The micro-processing is a processing method comprising forming a thin film of a photoresist on a silicon wafer, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the semiconductor substrate using the photoresist pattern as a protective film, thereby forming fine unevenness corresponding to the pattern on the surface of the substrate. However, in recent progress in high integration of semiconductor devices, there has been a tendency that shorter wavelength actinic rays are being used, i.e., ArF excimer laser beam (193 nm) has been taking the place of KrF excimer laser beam (248 nm). Along with this change, influences of random reflection and standing wave off a substrate have become serious problems. Accordingly, it has been widely studied to provide an anti-reflective coating between the photoresist and the substrate (Bottom Anti-Reflective Coating, BARC).
As the anti-reflective coating, inorganic anti-reflective coatings made of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon or α-silicon and organic anti-reflective coatings made of a light absorbing substance and a polymer compound are known. The former requires an installation such as a vacuum deposition apparatus, a CVD (chemical vapor deposition) apparatus or a sputtering apparatus. In contrast, the latter is considered advantageous in that it requires no special installation so that many studies have been made. For example, mention may be made of the acrylic resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule and the novolak resin type anti-reflective coating having a hydroxyl group being a crosslinking reaction group and a light absorbing group in the same molecule (see, for example U.S. Pat. Nos. 5,919,599 and 5,693,691).
The physical properties desired for organic anti-reflective coating materials include high absorbance to light and radioactive rays, no intermixing with the photoresist layer (being insoluble in photoresist solvents), no diffusion of low molecular substances from the anti-reflective coating material into the topcoat photoresist upon coating or heat-drying, and a higher dry etching rate than the photoresist (see, for example, Tom Lynch et al., “Properties and Performance of Near UV Reflectivity Control Layers”, US, in Advances in Resist Technology and Processing XI, Omkaram Nalamasu ed., Proceedings of SPIE, 1994, Vol. 2195, p. 225-229; G. Taylor et al., “Methacrylate Resist and Antireflective Coatings for 193 nm Lithography”, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 174-185; and Jim D. Meador et al., “Recent Progress in 193 nm Antireflective Coatings, US, in Microlithography 1999: in Advances in Resist Technology and Processing XVI, Will Conley ed., Proceedings of SPIE, 1999, Vol. 3678, p. 800-809).
On the other hand, in order to solve interconnection delay that has become clear with miniaturization in pattern rule of semiconductor devices in recent years, it has been considered to use copper as interconnect material, and to apply Dual Damascene process as interconnect forming method on the semiconductor device (see, for example U.S. Pat. No. 6,057,239). And, in Dual Damascene process, via holes are formed and an anti-reflective coating is formed on a substrate having a high aspect ratio. Therefore, the anti-reflective coating for use in this process is required to have control of coating performance of anti-reflective coating on a substrate of the periphery of hole, filling property by which via holes can be filled without gap, flattening property by which a flat coating can be formed on the surface of substrate, and the like in addition to the above-mentioned properties.
However, it is difficult to apply organic material for anti-reflective coating on a substrate having a high aspect ratio, and in recent years, material with particular emphasis on filling property or flattening property, that is, gap fill material has been developed (see, for example JP 2000-294504 A, WO 02/05035, JP 2002-190519 A, and JP 200247430 A).
And, it comes to be discussed a process in which two layers of an inorganic or organic anti-reflective coating having a high absorbance for light or radiation and a gap fill material for lithography for flattening are used. In the process, a gap fill material is applied on a substrate having a high aspect ratio, holes thereon are filled and the surface of the substrate is flattened. And, on the gap fill material, an organic anti-reflective coating or photoresist is formed.
The gap fill material for lithography mentioned above is Gap-Filling material, that is, a filler or a flattening agent. The advantages of the process reside in that because unevenness on a substrate is flattened by the gap fill material, a photoresist formed thereon comes to have an even film thickness and consequently a high resolution is obtained in lithography process.
In addition, the gap fill material has a high dry etching rate as it contains no compound having light absorption characteristics that is contained in an anti-reflective coating. Thus, the gap fill material shows a high etching selection ratio with the photoresist in etching process, and decrease in film thickness due to the etching of photoresist can be inhibited, and adverse effects on the underlaid substrate in the etching process can be inhibited.
Characteristic properties required for gap fill material for lithography are as follows: a gap fill material is insoluble in a solvent used for a photoresist (no intermixing with a photoresist causes); there is no low molecular matter diffused from a gap fill material layer to an overlaid photoresist or anti-reflective coating upon coating or heat-drying; it has a higher dry etching rate than a photoresist; and the surface of a substrate with a high aspect ratio (unevenness) can be flattened. And, any gap fill material for lithography satisfying all of these requirements is desired.
Taking the above-mentioned present status into account, the present inventors have eagerly studied, and as a result of it, found that a composition in which an acrylic polymer or a methacrylic polymer containing low molecular weight components in a low content is contained as a constituent component is suitable for a material for forming a gap fill material, and they completed the present invention.
The present invention relates to a gap fill material forming composition that is used in manufacture of semiconductor device by a method comprising coating a photoresist on a semiconductor substrate having a hole with a high aspect ratio that is used for example in dual damascene process, and transferring an image to the semiconductor substrate by use of lithography process.
An object of the present invention is to provide a gap fill material forming composition that can be used in such a lithography process in manufacture of semiconductor device. In addition, another object of the present invention is to provide a gap fill material that causes no intermixing with a photoresist layer, has a high dry etching rate compared with the photoresist, causes no diffusion of low molecular substances into the overlaid photoresist or anti-reflective coating upon coating or heat-drying, can accomplish a high flattening property to a substrate having a high aspect ratio (unevenness), and has an excellent filling property to holes; and a gap fill material forming composition for forming the above-mentioned gap fill material. Also, further object of the present invention is to provide a method for forming a gap fill material for lithography by use of a gap fill material forming composition, and a method for forming a photoresist pattern.